The talented reliever struggles in the loss to Pittsburgh.

PHILADELPHIA — — Charlie Manuel believes Phillippe Aumont has "all the potential in the world" and is going to be a "very good" major league pitcher someday.

But not without a few "growing pains" such as he showed in the Phillies' 6-4 loss Thursday to Pittsburgh.

The 24-year-old right-hander entered a 3-3 tie in the eighth inning and struck out the first hitter he faced.

But he hit Cliff Barnes on the next pitch, then ran a 3-0 count before giving up a single, the first of three straight hits that produced three Pirate runs.

"I've talked about growing pains," Manuel said when asked about Aumont. "You've seen when he's good, and you've seen when he struggles at times."

The Phillies manager believes the 6-foot-7, 260-pounder has the complete package: big, strong, with a good breaking ball and a fastball in the mid-90s, "97, 98 even."

Pittsburgh's three hits were one shy of the total Aumont had given up all year in 61/3 inning coming into the game. But he's shown a lack of command — he didn't walk anyone Thursday but has six walks, runs deep counts, and he's now hit a batter.

"Those growing pains, that's what you're going to see out of him for a while," Manuel said. "He's got to get to a place where he feels totally relaxed and comfortable, and pitch up to his potential."

Rehabbing Ruiz: Carlos Ruiz will join Reading Friday and Saturday for his final two tune-ups before joining the Phillies on Sunday in New York.

Ruiz's 25-game suspension for testing positive for a banned stimulant late last season ends Saturday.

Under baseball rules, Ruiz is allowed to play five official minor league games before his reinstatement. He joined Clearwater on Tuesday and went 1-for-8 with a home run and two walks in his first two games.

"Ruiz is a huge part of our team," pitcher Cliff Lee said. "He was obviously our best player last year. Getting him back can only help — his bat, his game-calling, his leadership behind the plate is definitely something that can help us, no doubt."

Ruiz's return means the Phillies will likely drop one of the two catchers currently on the active roster — Erik Kratz or Humberto Quintero — as well as make a move to get Ruiz back on the 40-man roster. Entering Thursday's game Kratz was hitting .185 (12-for-65) with two home runs and seven RBIs (tied for second on the team) in 20 games. He had also thrown out two of 10 would-be base stealers.

Quintero, who has become Roy Halladay's personal catcher in Ruiz's absence, was hitting .313 (5-for-16) with two RBIs in six games. He has yet to throw out a base stealer in three attempts.

'Antsy' Lee gets caught: Lee got his second hit of the season, an infield single, when Pirates pitcher James McDonald forgot to cover first base on a bouncer behind the bag.

A few pitches later, Lee took off for second a bit too early and was caught stealing, 1-6.

"Basically, I had it," said Lee, who has one steal in each of the past two seasons. "I got a little antsy."

Manuel said he's talked to Lee about taking off when the first baseman plays off the bag the way Gaby Sanchez was. Sanchez was playing about 10 feet off the bag.

"If he had just kept his walking lead and just waited until the guy threw the ball, he'd have definitely stole the bag."

Lee got a loud ovation as he trotted back to the dugout. Asked if he heard it, Lee said he didn't notice, adding that he was "more frustrated at giving them a free out."

Oh, say … : The women's choir from the Lehigh Valley Charter High School for the Arts of Bethlehem performed the national anthem.

On deck: After the game, the Phillies bused to New York for a weekend series with the Mets at CitiField, followed by a two-game series in Cleveland after an off day Monday. They return home Thursday for a weekend four-game series with Miami, followed by a West Coast trip to San Francisco and Arizona.